ISPSoft User Manual The X devices and the Y devices in the PLC are contacts connected to the equipment. The X device addresses and the Y device addresses are related to the wiring of the equipment. Users have to specify the device addresses by themselves. Besides, it is suggested that the X devices and the Y devices should be created in the global symbol table although some X devices and Y devices are only used in a certain POU. After the X devices and the Y device are created in the global symbol table, the subsequent maintenance such as changing the wiring and accessing the contacts in the additional program will be more convenient to users.
However, it is not necessary for users to create the X devices and the Y devices in the global symbol table. The users can decide by themselves. Owing to the fact that M0, M1, and M3 are used in the different POUs, the symbols correspond to the three flags are declared in the global symbol table. Users do not need to assign device addresses to the symbols, and therefore the system assigns device addresses to them. The number of parts which are conveyed is stored in D0, and D0 is only used in the COUNTING . As a result, the symbol corresponding to D0 is declared in the local symbol table in the COUNTING , and the system assigns a device address to D0.
6-44 Original devic e Identifier Address specified Declaration position Function name D0 CNT DT _ A device address is assigned automatically. Local symbol table Number of parts which are conveyed